GB1604114A - Derailleur assembly for a cycle - Google Patents

Description

PATENT SPECIFICATION

( 21) Application No 20575/78 ( 22) Filed 18 May 1978 ( 31) Convention Application No's 52/059211 ( 32) Filed 20 52/130394 U 27 52/130393 U 27 ( 33) Japan (JP) ( 44) Complete Specification Published 2 Dec 1981 ( 51) INT CL 3 B 62 M9/12 ( 52) Index at Acceptance F 2 D 7 A 4 ( 11) 1 604 114 May 1977 Sep 1977 ' -.

Sep 1977 in ( 54) A DERAILLEUR ASSEMBLY FOR A CYCLE ( 71) We SHIMANO INDUSTRIAL COMPANY LIMITED, a corporation organized under the laws of Japan, of 77, 3-cho, Oi-matsu-cho, Sakai, Osaka, Japan, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:

The invention relates to a derailleur for a cycle.

The derailleur of the invention is intended for use with a multi-sprocket assembly on the rear hub of a cycle so that a drive chain may be shifted to any selected one of the sprockets.

A conventional derailleur for this purpose comprises a base member fixed to the cycle, a movable member movable with respect to the base number axially of the rear hub of the cycle and a chain-shift member pivotally mounted upon the movable member A tension sprocket and a guide sprocket are rotatably mounted on the chain-shifting member and meshed with the drive chain of the cycle Normally, the sprockets of the multi-sprocket assembly are arranged in decreasing order of diameter (increasing order of gear ratio) outwardly along the hub and the derailleur is disposed axially outwardly of the smallest sprocket A control cable attached to the derailleur controls the derailleur to shift the chain axially inwardly against the bias of a return spring, shifting of the chain in the opposed direction being effected by the action of the return spring.

A typical prior art chain-shift member for a derailleur is shown in Figure 25 of the accompanying drawings and comprises two parallel plates a, and a 2 between which are sandwiched the tension and guide sprockets p, and P 2 respectively The plate a, lies axially outwardly of the tension and guide sprockets and serves to guide the chain.

However, because the spacing between the plates a, and a 2 is much larger than the width of the chain, when the chain-shift member is moving the chain between the various sprockets of the multi-sprocket assembly on the rear hub, the chain tends to be deflected from its proper course over the tension and guide sprockets and to contact one of the plates a, and a 2 This tends to make gear-changing very noisy and may lead to difficulties in effecting proper gear changes If attempts are made to reduce these difficulties by decreasing the spacing between the plates a, and a 2, the chain tends to contact one or other of the plates even when gear-changing is not being effected, thereby hindering smooth and quiet running of the chain.

The present invention seeks to provide a derailleur which reduces or eliminates one or more of the aforementioned problems and renders gear changing quieter and smoother.

Accordingly, the invention provides a derailleur for shifting a drive chain to any one of a plurality of sprockets, of a multispeed sprocket assembly, said derailleur comprising: a base member; a movable member movable relative to said base member; a chain shift member pivotally connected to said movable member, said chain shift member comprising a single plate and carrying a tension sprocket and a guide sprocket mounted so as to be rotatable independently of each other, said tension and guide sprockets having teeth for meshing with said drive chain in use of the derailleur; a guide member; mounting means for mounting said guide member on said chain-shift member so that said guide member is movable between a first position for permitting disengagement of said drive chain from said guide sprocket and removal from the derailleur, in use of said derailleur, and a second position for preventing disengagement of said drive chain from said guide 1 604 114 sprocket, in use of the derailleur, by means of an engagement portion of the guide member disposed radially outwardly of the guide sprocket teeth, optionally in coS operation with tension in the chain, said first portion being generally radially outward of said second position with reference to said guide sprocket.

The guide member is preferably slidable relative to the chain-shift member radially of the guide sprocket To render the guide and chain-shift members slidable relative to one another, preferably one of the guide member and chain-shift member has a bore therethrough, the other of said members has an elongate slot therethrough and the derailleur includes a retaining member disposable through said bore and slot for retaining the said two members in any one of a plurality of different positions relative to one another.

Alternatively, the guide member may be pivotally mounted on the chain-shift member In a preferred form of derailleur of this type, the guide member is pivotally mounted on the chain-shift member for pivoting about an axis which does not pass through the guide sprocket, a pin is mounted on one of the guide member and chain-shift member so as to be movable generally parallel to the axis of the guide sprocket, and in the other of the guide member and chain-shift member is provided a cut-out for receiving a part of the pin, when said guide member is disposed in its second, radially inward, position, said pin being movable between a locking position with said part thereof received in said cut-out, and a released position in which said guide member is movable from its radially inward position Desirably, in such a derailleur, the pin has at one end thereof a head portion of enlarged diameter intermediate its ends, and the cut-out is generally keyhole shaped with a larger diameter portion for receiving therein said pin head portion in the locking position of the pin, and open-sided at a narrower portion thereof for permitting passage through said narrower portion of a smaller diameter portion of the pin but not said head portion thereof in the released position of said pin, there being also provided a spring means arranged for biasing said pin into its locking position.

When the axis of rotation of the tension sprocket lies substantially perpendicular to the plate of the chain-shift member, the preferred form of guide member comprises a first portion extending substantially parallel to said plate and a second portion connected at one end thereof to the first portion and extending substantially perpendicular to said plate, the opposed end of the second portion being connected to the engagement portion of the guide member, which engagement portion extends radially inwardly towards the axis of the guide sprocket.

With such a guide member, the part of the engagement portion thereof nearest the guide sprocket may either lie adjacent the tips of the teeth on that sprocket so as to pass between the link plates of a drive chain engaged with said teeth, or be disposed on the opposed side of the guide sprocket from the chain-shifting member so as to abut or lie adjacent the outer surfaces of the link plates on one side of a drive chain engaged with the teeth on the guide sprocket.

The invention also extends to a cycle incorporating a derailleur of the invention.

Preferred embodiments of the invention will now be described in more detail, though by way of illustration only, with reference to the accompanying drawings, in which like reference numbers indicate like parts and in which:

Figure 1 is a side elevation of part of a first derailleur of the invention; Figure 2 is a view of the part of the derailleur shown in Figure 1 from the opposed side thereof; Figure 3 is a top plan view of the part of the derailleur shown in Figures 1 and 2; Figure 4 is a rear elevation, partly in section, of part of the derailleur shown in Figures 1 and 2, and shows the derailleur assembly in its operating position; Figure 6 is a side elevation of part of the chain-shift member shown in Figure 1 from the same side as that Figure; Figure 7 is a perspective view of the guide member shown in Figures 1 to 5; Figure 8 is a side elevation, corresponding to that of Figure 1, of part of a second derailleur of the invention; Figure 9 is a view of the part of the derailleur shown in Figure 8 from the opposed side thereof; Figure 10 is a rear elevation, partly in section, of part of the derailleur shown in Figures 8 and 9, and shows the derailleur in its operating position; Figure 11 is a view similar to Figure 10 but showing the manner of engaging a drive chain with the sprockets of the derailleur:

Figure 12 is a perspective view of the guide member shown in Figures 8 to 11:

Figure 13 is a side elevation corresponding to that of Figure 1 of part of a third derailleur of the invention:

Figure 14 is a view of the part of the derailleur shown in Figure 13 from the opposed side thereof; Figure 15 is a top plan view of the part of the derailleur shown in Figures 13 and 14:

Figure 16 is a rear elevation, partly in section, of the part of the derailleur shown in Figures 13 to 15; Figure 17 is a side elevation, from the 1 604 114 same side as in Figure 13, of the chain-shift member shown in Figures 13 to 16; Figure 18 is a perspective view of the guide member shown in Figures 13 to 17; S Figure 19 is a side elevation, similar to that of Figure 13 but showing the method of engaging the drive chain of the derailleur; Figure 20 is a rear elevation, partly in section, of part of a fourth derailleur of the invention; Figure 21 is a side elevation of part of a fifth derailleur of the invention; Figure 22 is a top plan view of the part of the derailleur shown in Figure 21; Figure 23 is a rear elevation illustrating generally the use of a derailleur of the invention, but in which the guide member mounting is shown only schematically; Figure 24 is a side elevation of the derailleur of Figure 23; and Figure 25 is, as already mentioned, a rear elevation of part of a prior art derailleur.

Figures 23 and 24 show generally a derailleur of the invention, but with the guide member mounting not shown.

Thus in general a derailleur of the invention comprises a base member 2, on which is pivotally mounted a bracket 1 by means of which the base member 2 can be secured to the rear hub H (Figure 23) of a cycle, a pair of link members 3 (only one of which is shown in Figure 23) and a movable member 4 Each of the link members 3 is pivotally mounted at its one end upon the base member 2 and at its opposed end on the movable member 4 so that the base member, the two link members and the movable member together form a parallelogram linkage When the bracket 1 is mounted upon the rear hub H, the pivoting of the link members 3 renders the movable member 4 movable relative to the base member 2.

(The base members, link members and movable members of the various derailleurs of the invention shown in Figures 1 to 22 are substantially identical to the corresponding members shown in Figures 23 and 24 but are omitted from Figures 1 to 22 for the sake of clarity) A chain-shift or shift member 7 is mounted upon the movable member 4 by means of a pivot 10 The shift member 7 is formed of a single flat plate and carries a tension sprocket 5 and a guide sprocket 6, these two sprockets being mounted on the shift member 7 by means of sprocket shafts 51 and 61 respectively which pass through bores in the shift member 7 so as to be rotatable independently of one another about axes perpendicular to the plane of the shift member 7 and each of the sprockets 5 and 6 bearing teeth capable of meshing with the drive chain of a cycle.

The derailleur includes a guide member (generally designated 8) which in accordance with the invention is movable relative to the shift member 7 though this feature is not shown in Figures 23 and 24 The guide member 8 comprises a first portion 81 extending in the plane of the shift member 7, a second portion 82 connected at its one end to the first portion 81 and extending perpendicular to the said plane, and an engagement portion 83 which is connected to the opposed end of the second section 82 and which extends radially inwardly towards the axis of the guide sprocket 6, so that the part of the engagement portion 83 nearest the guide sprocket 6 lies adjacent the tips of the teeth on that sprocket so as to pass between the link plates Cl and C 2 of a drive chain C engaged with said teeth, the engagement portion 83 of course having a thickness smaller than the spacing between the link plates on opposed sides of the chain C The engagement portion 83 of the guide member 8 thus lies radially outwardly of the teeth on the guide sprocket 6 and is capable of retaining the drive chain C engagedwith the teeth on the guide sprocket 6 once the drive chain has been engaged with said teeth.

Finally, the derailleur shown includes a chain guide plate 30 disposed axially of the tension sprocket 5 on the opposed side thereof from the shift member 7.

In use, as shown in Figure 23, the derailleur of the invention may be mounted on a bicycle, the bracket 1 being secured by means of a nut to the rear hub H of the bicycle axially outwardly of a set of sprockets of a multi-sprocket assembly S thereon.

The sprocket assembly S is arranged so that the smallest sprocket S, lies adjacent the derailleur whilst the largest sprocket 52 is closest to flange A which is one of a pair of flanges A and B carried on the hub H A control wire (not shown), forming part of a control cable, may be pulled to move the movable member 4 axially inwardly of the hub H so that the shift member 7 is shifted from the position shown in full lines in Figures 23, in which position the chain (not shown) of the bicycle, which is engaged with the guide and tension sprockets 5 and 6, is also engaged with the smallest sprocket So, to that shown in broken lines in Figure 23 (in which position the chain is engaged with the largest sprocket 52), against the bias of a return spring (not shown) When the control wire is moved in the opposed direction, the return spring moves the movable and shift members axially outwardly of the hub H.

Thus, by use of the derailleur the chain may be engaged with any desired one of the sprockets or the sprocket assembly S During such shifting of the chain, the engagement portion 83 of the guide member 8 prevents the chain being deflected from its proper course; if the chain C should tend to move axially outwardly from the guide 1 604 114 sprocket 6, the engagement portion 83 will abut the rollers C 3 of the chain C, thereby keeping the chain engaged with the guide pulley 6 The tension sprocket 5 also tends S to resist disengagement of the drive chain by radially outward movement of the chain from the tension and guide sprockets, by means of the force exerted by a chain tensioning spring 90 wound around the shift member mounting pivot 10 as shown in Figure 23 In this way the resistance to chain shifting is reduced and contact of the chain with the inward face of the shift member 7, which is responsible for the noises generated during gear shifting by prior art derailleurs is substantially prevented.

Furthermore, the provision of the guide member 8 in the derailleur eliminates the need for the second, axially-inward plate a 2 of the prior art derailleur assembly shown in

Figure 24, since the guide member 8 prevents the chain from striking the spokes D in Figure 23 The elimination of the plate a 2 renders it possible to mount the derailleur assembly of the invention and the sprockets S closer to the flange A by a distance equal to the thickness of the plate a 2 The presence of the chain guide plate 30 does not interfere with the axially-inward mounting of the assembly since the plate 30 is well spaced from the axis of the hub H This reduction in the axial spacing between the sprockets S and the rim R reduces the torque about an axis perpendicular to the plane of Figure 23 passing through the centre of the hub H exerted by the chain tension on the hub H and spokes D thereby increasing the working life of the spokes and the stability of the bicycle's rear wheel.

In accordance with the present invention, the derailleur, parts of which are shown in Figures 1 to 7 of the accompanying drawings, has its guide member 8 pivotally mounted on its shift member 7 by means of a pivot 11 so as to pivot about an axis which does not pass through the guide sprocket 6.

One end of the pivot 11 is fixed in a bore 71 (best seen in Figure 6) in the shift member 7, whilst the opposed end of the pivot is received in a bore 84 (see Figure 7) formed in the first section 81 of the guide member 8.

A bore 73 (Figures 1 and 6) receives the pivot 10 by means of which pivot 10 the shift member 7 is mounted on the movable member (not shown) of the assembly.

The guide member 7 is movable between a first position for permitting disengagement of the chain from the guide sprocket and a second position for preventing disengagement of the chain from the guide sprocket 6.

As may be seen from the drawings the first position is generally radially outward of the first position relative to guide sprocket 6 though these positions are not necessarily on the same radius as indeed they are not in this particular embodiment.

In the second, radially inward, position (as shown in Figure 3) the engagement portion 83 of the guide member 8 lies adjacent a chain engaged with the guide sprocket 6 and serves to retain the chain engaged with the teeth on said guide sprocket 6 The guide member 8 is secured in this radially inward position by a pin 9 mounted in bores 85 a and 85 b formed in the first portion 81 and in the engagement portion 83 respectively of the guide member 8, (see especially Figures 4, 5 and 7), this pin 9 being movable parallel to the axis of rotation of the guide sprocket 6 At one end (to the left in Figures 7 and 8) of the pin 9 is formed a head 93 and a compression spring 12 is disposed with one abutting the head 93 (which thus constitutes an abutment section of the pin) and its opposed end abutting the first section 81 of the guide member 8, so as to bias the pin 9 to the left in Figures 8 and 9.

A ring 91 is fixed by means of a stop member 92 to the pin 9 intermediate its end to form a head portion of enlarged diameter As best seen in Figure 6, a generally key-hole shaped cut-out 72 is provided in the shift member 7, this cut-out 72 having a, larger diameter, portion 72 b and a narrower portion 72 a extending to the periphery of the shift member 7 and being open-sided thereat The larger portion 72 b is formed for receiving therein the head portion 91 with a relatively close fit Although the head portion 91 cannot pass through the narrower portion 72 a of the cut-out 72, a narrower part of the pin 9 lying between the ring 91 and a head 93 can do so As shown in Figure 4, which shows the guide member 8 in its radially inward position, in this position the head portion 91 lies within the larger diameter portion 72 b of the cut-out 72 and abuts the first section 81 of the guide member 8, so that the guide member 8 cannot pivot relative to the shift member 7 and is thus secured in this position.

The provision of the pivotable guide member 8 facilitates the initial installation of the chain C and engagement thereof with the tension and guide sprockets 5 and 6 respectively In order to insert the chain C, the pin 9 is pushed against the bias of the spring 12 to the right in Figure 7 until it assumes the released position shown in Figure 8, in which the head portion 91 is clear of the cut-out 72 The guide member 8 may now be pivoted outwardly and downwardly relative to the shift member 7 from its radially inward position, shown in full lines in Figures 1 and 2, to the position shown in broken lines therein, the intermediate portion of the pin 9 between the head portion 91 and the head 93 sliding down the first section 72 a of the cut-out 72 during this 1 604 114 pivoting The guide member 8 is now well-spaced from the guide sprocket 6 and the chain C can easily be inserted and engaged with the sprockets 5 and 6.

To return the guide member 8 to its radially inward normal operating position, the pin 9 is again moved against the bias of the spring 12 and then the guide member 8 is pivoted anticlockwise in Figure 4 until the head portion 91 lies adjacent the second section 72 b of the cut-out 72 The pin 9 is now released, thus permitting the head portion 91 to enter the larger-diameter portion 72 b of the cut-out 72 and retain the guide member 8 in its operating position.

The second derailleur of the invention, parts of which are shown in Figures 8 to 12, has its guide member 8 pivotally mounted upon its shift member 7 by means of the pivot 10 through which its shift member 7 is pivotally mounted upon its movable member (not shown) The pivot 10 extends through a bore 73 provided in the shift member 7, the end of the pivot 10 lying within the bore 73 being enlarged so that the shift member 7 cannot slip off that end of the pivot 10 Between the shift member 7 and a shoulder on the pivot 10 is held a flanged washer 40 fixed relative to the pivot 10, the washer 40 being rotatably received within a bore 84 provided in the first section of the guide member 8, thus rendering the guide member 8 pivotable about the axis of the pivot 10 relative to the shift member 7.

A pin 9 is slidably mounted within a bore 74 in the shift member 7 and can slide parallel to the axis of the guide sprocket 6.

The pin 9 has a head 93 at its one end, a head portion 91 of enlarged diameter adjacent the head 93 and an abutment section or stop 92 at its opposed end A compression spring 12 has its one end abutting the stop 92 and its opposed end abutting the shift member 7, so that the spring 12 biases the pin 9 to the right in Figures 10 and 11.

In the guide member 8 is provided a generally key-hole shaped cut-out 86 (best seen in Figure 12) similar to the cut-out 72 of the above embodiment, with a larger diameter portion 86 b and a narrower portion 86 a which opens out at the periphery of the guide member 8 The cut-out 86 cooperates with the pin 91 in similar manner to that described above Thus to insert the chain C, the pin 9 is moved to the left from the position shown in Figure 10 (which, as mentioned above, shows the derailleur in its radially inward position) against the bias of the spring 12 until it assumes the position shown in Figure 11, in which the head portion 91 is clear of the cut-out 86 The guide member 8 may now be pivoted in the direction of the arrow in Figure 8 until it is sufficiently spaced from the guide sprocket 6, the portion of the pin 9 between the head portion 91 and the stop 92 sliding along the narrower portion 86 a of the cut-out 86 The chain C can now easily be engaged with the sprockets 5 and 6.

To return the guide member 8 to its operating position, the pin 9 is again moved against the bias of the spring 12 and then the guide member 8 is pivoted anticlockwise, as viewed in Figure 8, until the head portion 91 lies adjacent the second section 86 b of the cut-out 86 The pin 9 is now released, thus permitting the enlarged section to enter the larger diameter portion 86 b and retain securely the guide member 8 in its radially inward position.

Removal of the chain C from the sprockets 5 and 6 in the first and second derailleurs of the invention can of course be effected simply by reversing the above procedure.

Thus both installation and removal of the chain are quick, easy and require no tools.

In the third derailleur of the invention, parts of which are shown in Figures 13 to 19, the guide member 8 is again pivotally mounted on the shift member 7 by means of a pivot 11 which passes through a bore 84 in the guide member 8 and a bore 71 in the shift member 7 In this derailleur, however, the guide member 8 is provided with an extension 87 having a bore 87 a therethrough, this bore having secured therein one end of the shaft 51 on which the tension sprocket 5 rotates The extension 87 terminates in a chain guide plate 88 which, as best seen in Figure 16, is disposed alongside of the tension sprocket 5 on the side of the latter remote from the shift member 7.

The shift member 7 of this derailleur is detachable from the shaft 51, the shift member 7 being provided with a slot 75 closed at one end; this slot, as shown in Figure 19, can be releasably engaged with the shaft 51 Thus, in this derailleur the tension sprocket 5 is actually secured to the guide member 8 and can be releasably secured to the shift member 7 From Figures 13 and 14 it will be seen that the tension in a drive chain C engaged with the sprockets 5 and 6 urges the shaft 51 towards the closed end of the slot 75, thereby retaining the guide member 8 in its operating position in which its engagement portion 83 lies adjacent and radially outwardly of the teeth on the guide sprocket 6, as best seen in Figures and 16 However, to effect initial engagement of the chain C with the guide sprockets 6, the tension sprocket 5 is moved in the direction of the arrows in Figure 19, thereby moving the engagement portion 83 of the guide member 8 generally radially outwardly away from the guide sprocket 6 Although in this case the movement is not strictly in a radial direction, the position to which the guide member is moved is radially further out and the expression radially outwardly is 1 604 114 used in this sense.

The fourth derailleur of the invention, part of which is shown in Figure 20, differs from the third derailleur just described in that its shaft 51 is secured to its shift member 7, whilst the extension 87 of its guide member 8 is provided with a slot 89 closed at one end, this slot 89 being detachably engageable with the shaft 51 To move the engagement portion 83 of the guide member 8 away from the guide sprocket 6, the slot 89 is slipped off the shaft 51 and the guide member 8 pivoted about the pivot 11 relative to the shift member 7.

The third and fourth derailleurs of the invention eliminate the need for the retaining pin 9 in the first and second assemblies.

Finally, the fifth derailleur of the invention, parts of which are shown in Figures 21 and 22, has its shift member 7 slidable relative to its guide member 8 radially of the guide sprocket 6 A threaded bore is provided extending through the shift member 7, an elongate slot 20 extending radially of the guide sprocket 6 is cut through the first portion 81 of the guide member 8 and a retaining member in the form of a threaded bore, the head of this bolt 21 abutting the first portion 81 of the guide member 8 and retaining the guide member 8 fixed relative to the shift member 7 Obviously by unscrewing the bolt 21, moving the slot 20 relative thereto and screwing the bolt 21 back into position, the guide member 8 may be retained in any one of a plurality of differing positions relative to the shift member 7 Providing a threaded bore in the guide member 8 and a slot 20 in the shift member 7 would of course serve exactly the same purpose.

The fifth derailleur of the invention lacks the chain guide plate 30 shown in Figures 23 and 24 but instead, its guide member 8 is provided with an extension which terminates in a chain guide portion 8 a disposed radially outwardly of the tension sprocket 5.

Lastly, the engagement portion 83 of the guide member 8 of the fifth derailleur does not lie adjacent the tips of the teeth on the guide sprocket 6 Instead, the engagement portion 83 is disposed on the opposite side of the guide sprocket 6 remote from the shift member 7 so as to lie adjacent the outer surfaces of the link plates C 2 on one side of the drive chain C engaged with the teeth on the guide sprocket 6 (Alternatively, the engagement portion 83 may abut the outer surfaces of the link plates C 2) This type of engagement portion of the guide member may also be substituted for that shown in any of the above-described first to fourth derailleurs.

In the case of the fifth embodiment it can of course be seen that although the engagement portion 83 prevents disengagement of the chain C axially of the guide sprocket it does not do so with respect to disengage-ment radially of the guide sprocket This latter type of disengagement will of course be prevented by the tension in the chain due to the derailleur tension spring as referred to earlier above with reference to Figure 23.

Thus in this case the co-operation of the tension in the chain is necessary to fully prevent chain disengagement.

Claims (17)

WHAT WE CLAIM IS:-

1 A derailleur for shifting a drive chain to any one of a plurality of sprockets of a multi-speed sprocket assembly, said derailleur comprising: a base member, a movable member movable relative to said base member; a chain-shift member pivotally connected to said movable member, said chainshift member comprising a single plate and carrying a tension sprocket and a guide sprocket mounted so as to be rotatable independently of each other, said tension and guide sprockets having teeth for meshing with said drive chain in use of the derailleur; a guide member; mounting means for mounting said guide member on said chain-shift member so that said guide member is movable between a first position for permitting disengagement of said drive chain from said guide sprocket and removal from the derailleur, in use of said derailleur, and a second position for preventing disengagement of said drive chain from said guide sprocket, in use of the derailleur, by means of an engagement portion of the guide member disposed radially outwardly of the guide sprocket teeth, optionally in cooperation with tension in the chain, said first position being generally radially outward of said second position with reference to said guide sprocket.

2 A derailleur assembly as claimed in Claim 1, in which the guide member is movable relative to the chain-shift member substantially radially of the guide sprocket.

3 A derailleur as claimed in Claim 2, in which the mounting means is formed and arranged so that the guide member is slidable relative to the chain-shift member substantially radially of the guide sprocket.

4 A derailleur as claimed in Claim 3, in which one of the guide member and chainshift member has a bore therethrough, the other of said members has an elongate slot therethrough and the derailleur includes a retaining member disposable through said bore and slot for retaining the said two members in any one of a plurality of different positions relative to one another.

A derailleur as claimed in Claim 1, in which the mounting means is formed and arranged so that the guide member is pivotally mounted on the chain-shifting member.

6 A derailleur as claimed in Claim 5, in 7 1 604 114 7 which the guide member is pivotally mounted on the chain-shift member for pivoting about an axis which does not pass through the guide sprocket, a pin is mounted on one of the guide member and chain-shift member so as to be movable generally parallel to the axis of the guide sprocket, and in the other of the guide member and chain-shift member is provided a cut-out for receiving a part of the pin, when said guide member is disposed in its second, radially inward, position, said pin being movable between a locking position with said part thereof received in said cut-out, and a released position in which said guide member is movable from its radially inward position.

7 A derailleur as claimed in Claim 6, in which the pin has a head portion of enlarged diameter intermediate its ends, and in which the cut-out is generally key-hole shaped with a larger diameter portion for receiving therein said pin head portion in the locking position of the pin, and open-sided at a narrower portion thereof for permitting passage through said narrower portion of a smaller diameter portion of the pin but not said head portion thereof, in the released position of said pin, and in which is provided a spring means arranged for biasing said pin into its locking position.

8 A derailleur as claimed in Claim 5, in which the guide member is provided with an extension which engages a shaft on which the tension sprocket rotates.

9 A derailleur as claimed in Claim 8, in which the chain-shift member is detachable from said shaft.

A derailleur as claimed in any one of Claims 1 to 9, in which the axis of rotation of the tension sprocket lies substantially perpendicular to the plane of the plate, and in which the guide member comprises a first portion extending substantially parallel to said plane and a second portion connected at one end thereof to the first portion and extending substantially perpendicular to said plane, the opposed end of the second portion being connected to the engagement portion of the guide member, which engagement portion extends radially inwardly towards the axis of the guide sprocket.

11 A derailleur as claimed in Claim 10, in which the part of the engagement portion nearest the guide sprocket lies adjacent the tips of the teeth on that sprocket so as to pass between the link plates of a drive chain engaged with said teeth.

12 A derailleur assembly as claimed in Claim 10, in which the engagement portion of the guide member is disposed on the opposed side of the guide sprocket from the chain-shift member so as to abut or lie adjacent the outer surfaces of the link plates on one side of a drive chain engaged with the teeth on the guide sprocket.

13 A derailleur as claimed in any one of the preceding claims, which derailleur includes a chain guide plate disposed axially of the tension sprocket on the opposed side thereon from the chain-shift member.

14 A derailleur as claimed in any one of the preceding claims, in which the chainshift member is provided with a chain guide portion disposed radially outwardly of the tension sprocket.

A derailleur as claimed in any one of the preceding claims, mounted upon a cycle, the drive chain of the cycle being engaged with the teeth on the guide and tension sprockets of the derailleur.

16 A derailleur substantially as herein described, with reference to and as illustrated in any of Figures 1 to 7, Figures 8 to 12, Figures 13 to 19, Figure 20 or Figures 21 and 22, alone or in combination with Figures 23 and 24 of the accompanying drawings.

17 A cycle incorporating a derailleur as claimed in any one of the preceding claims.

CRUIKSHANK & FAIRWEATHER, Chartered Patent Agents, 19 Royal Exchange Square, Glasgow, G 1 3 AE, Scotland.

Agents for the Applicants.

Printed for Her Majesty's Stationery Office.

by Croydon Printing Company Limited Croydon Surrey, 1981.

Published by The Patent Office 25 Southampton Buildings.

London, WC 2 A l AY, from which copies may be obtained.

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